Pictured is an open pack of Camel cigarettes purchased Friday, Nov. 30, 2012, in Chicago. New tobacco products have come nearly to a halt in the U.S. because regulatory reviews for thousands of applications required by a 2009 law are taking much longer than the law requires. Though it might sound like good news from a health perspective, the halt demonstrates how tricky it is to start regulating an industry.(AP Photo/Charles Rex Arbogast)

Photo: Charles Rex Arbogast, Associated Press

Pictured is an open pack of Camel cigarettes purchased Friday, Nov....

Va. - Tobacco companies have introduced almost no new cigarettes or smokeless tobacco products in the United States in more than 18 months because the federal government has prevented them from doing so, an Associated Press review has found.

It's an unprecedented pause for an industry that historically has introduced dozens of new products annually, and reflects its increasingly uneasy relationship with the Food and Drug Administration, which in 2009 began regulating tobacco.

Officials at the FDA say the reviews of applications for new products have taken so long because of "significant deficiencies" and because the agency is taking extra care in reviewing products that pose public health risks.

Industry executives say cigarettes haven't changed in any meaningful way, and the delays don't make sense. They say the changes are as simple as a brand name change, cigarette filters or, in some cases, different packaging.

Since June 2009, when the law allowing the agency to regulate tobacco went into effect, the tobacco industry has submitted nearly 3,500 product applications, according to data obtained under a Freedom of Information Act request. While none have been ruled upon, the vast majority of these products are already being sold.

A grandfather clause in the law allows products introduced between February 2007 and March 2011 that are similar to those previously on the market to be sold while under review. They can be removed from store shelves if they don't pass muster with the agency.

Part of the delay problem is that the tobacco industry is still learning how to deal with being regulated.

"They have the burden of demonstrating that new products and product changes won't increase youth tobacco use, won't increase toxicity and won't wrongly deter people from quitting," said Matt Myers, president of the Campaign for Tobacco-Free Kids.